This application is the U.S. National Phase under 35 U.S.C. xc2xa7371 of International Application PCT/AP99/01113, filed Mar. 8, 1999, which claims priority based on JP 1998-57246, filed Mar. 9, 1998.
The present invention relates to a process for producing metalloporphyrins. More particularly, the present Invention relates to a process for producing metalloporphyrins containing transition metals inserted into the porphyrin ring which are useful as functional materials, such as photoresponsive materials and organoelectronic materials.
With regard to porphyrins discovered as substances Involved in photosynthesis, studies are In progress on the structural control, chemical modification, and exploitation thereof as photoresponsive materials or electronic materials.
In the course of these studies, metalloporphyrins containing transition metals inserted into the porphyrin ring are gathering attention.
However, in the production of such porphyrin-metal complexes. the insertion of a transition metal ion into the porphyrin ring has been found to be difficult and because of the high temperature conditions required [a) Meumier et al. Bull. Soc. Chim. Fr. 1994, 131, 78-88. b) Collman et al. J. Am. Chem. Soc 1995, 117, 692-703. c) Ohkubo et al. J. Mol. Cat., 1994, 91, 7-17. d) Guilard et al. J. Am. Chem. Soc. 1994, 116, 10202-10211. e) Meumier et al. Inorg. Chem 1991, 30, 706-711. f) Saveant et al. J. Am. Chem. Soc. 1991, 113, 1586-1595. g) Quici et al. J. al. J. Mol. Cat. A: Chemical 1996, 113, 77-86] and the inert atmosphere required for conducting the reaction [a) Meumier and Momenteau et al. J. Mol. Cat. A: Chemical 1996, 113, 23-34. b) Tsuchida et al. J. Chem. Soc. Dalton Trans. 1990, 2713-2718. c) Collman et al J. Am. Chem. Soc. 1975, 97, 1427-1439. d) Groves et al. J. Am. Chem. Soc. 1983, 105, 5791-5796.], among other restrictions, it has been impossible to synthesize transition metal-porphyrin complexes easily under mild conditions using transition metals and porphyrins in desired combinations.
Therefore, an object of the present invention Is to solve the problem of those prior arts and to provide a novel technology for producing metalloporphyrins by which a transition metal ion can be inserted into the porphyrin ring of an arbitrary hydrophobic or hydrophilic porphyrin compound expediently with high selectivity, for example by conducting the necessary reaction at room temperature.
Accomplished in the above state of the art, the present invention is directed, in a first aspect thereof, to a process for producing a metalloporphyrin containing a transition metal inserted into the porphyrin ring which comprises dissolving a porphyrin compound and a transition metal salt each in an independent solvent, combining the two solutions, and reacting them in the presence of a basic substance or basic substances.
In connection with this first aspect, the present invention provides, in a second aspect thereof, a process for producing a metalloporphyrin wherein the basic substance is supplied in the form of the solvent for dissolving the porphyrin compound; in a third aspect, a process for producing a metalloporphyrin wherein the basic substance is added at the stage of mixing the solutions; in a fourth aspect, a process for producing a metalloporphyrin wherein said reaction is carried out at a temperature not over 40xc2x0 C.; in a fifth aspect, a process for producing a metalloporphyrin wherein the transition metal salt is an inorganic salt of iron (Fe) or manganese (Mn); and in a sixth aspect, a process for producing a metalloporphyrin wherein the porphyrin is an optionally substituted hydrophobic or hydrophilic porphyrin compound.
While the present invention has the above features, its technical essence lies in enabling synthesis of various metalloporphyrins in a homogeneous reaction system under mild conditions and with high selectivity.
The working modes of the present invention are now described.
First, in the process for producing a metalloporphyrin according to the present invention, hydrophobic or hydrophilic porphyrin compounds having a porphyrin ring or rings and optionally bearing various substituent groups can be used as starting materials. These starting materials have structures permitting insertion of a transition metal ion.
The fundamental structure involved may be visualized as having a porphyrin ring of the following formula: 
(wherein R1xcx9cR12 each represents a hydrogen atom or an organic group).
As examples of said organic group for R1xcx9cR12, there can be mentioned hydrocarbon groups, whether acyclic or cyclic and whether saturated or unsaturated, such as alkyl, alkenyl, cycloalkyl, phenyl, naphthyl, etc., which may optionally be substituted by various functional groups such as halogen, hydroxy, alkoxy, alkoxycarbonyl, carboxy, amido, amino, nitro, cyano, carbamate, urea, sulfonyl, sulfenyl, phosphenyl, phosphinyl, sulfide, thioether, thioester, etc.; heterocyclic groups such as pyridyl, piperidyl, azino, azolyl, imidazolyl, triazinyl, furyl, carbazolyl, etc.; organic groups having a sugar moiety or a cyclodextrin or porphyrin ring.
Furthermore, R1xcx9cR12, between adjacent ones, may form a heterocycle or a carbocycle with or without the intermediary of a heteroatom or heteroatoms. The transition metal salts to be complexed with such porphyrin compounds may be any of various salts of transition metals that are able to make at least two formal bonds. Thus, the transition metal includes but is not limited to Fe, Ni, Co, Cu, Zn, Ti, Mn, Mo, V, Zr, Cd, Sb, Cr, and Nb. As far as the present invention is concerned, Fe (iron) and Mn (manganese) can be mentioned as preferred transition metals.
The salt of such a transition metal may be any of various inorganic acids, such as hydrochloric acid, sulfuric acid, phosphoric acid, etc., and various organic acids. Particularly preferred are salts of inorganic acids, such as FeCl2 and MnCl2.
In the process according to the present invention, said transition metal salt is preferably used in a molar excess over the starting material porphyrin. The molar ratio may for example be 1.1xcx9c30, more preferably 2xcx9c25, and still more preferably 5xcx9c20.
In conducting the reaction, the starting material porphyrin and the transition metal salt are dissolved each in an independent solvent and the resulting solutions are combined. This procedure of dissolving the porphyrin and the transition metal salt in independent solvents and combining the solutions is an indispensable requisite in carrying out the process of the present invention.
The solvent for dissolving the starting material porphyrin can be generally selected according to whether the particular porphyrin is hydrophobic or hydrophilic. Moreover, a solvent having a high solubilizing power for the porphyrin and capable of providing a homogeneous solution is selected. Taking a hydrophobic porphyrin as an example, hydrophobic organic solvents are selectively used. Thus, halogenated hydrocarbons, aromatic hydrocarbons, nitriles, etc. may be mentioned. In particular, halogenated hydrocarbons such as chloroform (CHCl3), dichloromethane (CH2Cl2), etc. constitute a preferred class of organic solvents.
On the other hand, when the starting material porphyrin is hydrophilic, hydrophilic solvents such as water, alcohols, amines, nitrogeneous heterocyclic compounds, etc. can be generally employed.
The homogeneous solutions thus prepared are combined. In this combined solution, a basic substance or basic compound is caused to be present. This presence of a basic substance can be assured, for example by using a basic substance as the solvent when it is an amine or a nitrogeneous heterocyclic compound or by adding a basic substance to the combined solution, or even by using such procedures in combination.
The relative amount of the solvent and basic substance is not particularly restricted but can be freely selected within the range assisting in the transition metal insertion reaction according to the invention and not adversely affecting the process.
The basic substance which can be used includes nitrogen-containing heterocyclic compounds such as pyridine, methylpyridine, dimethylpyridine, diazines, methyldiazines, pyrazine, ethylpyrazine, pyrimidine, piperazine, morpholine, etc.; aliphatic amines such as diethylamine, ethylenediamine, tert-butylamine, etc.; basic resins; and inorganic bases.
In particular, organic basic substances such as 2,6-lutidine are preferred.
The reaction temperature may generally be not over 40xc2x0 C. This limit of 40xc2x0 C. may at times be exceeded but It does not happen that this limit is exceeded in any remarkable measure. Actually, the reaction can be conducted at room temperature or in the neighborhood thereof. In this respect, the process of the invention is basically different from the conventional processes.
After completion of the reaction, the reaction product can be isolated and purified by various procedures such as chromatography, precipitation, recrystallization, etc.